Journal articles on the topic 'Duct wall'
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1
Hawwa, Muhammad A. "Sound Propagation in a Duct with Wall Corrugations Having Square-Wave Profiles." Mathematical Problems in Engineering 2015 (2015): 1–8. http://dx.doi.org/10.1155/2015/516982.
Abstract:
Acoustic wave propagation in ducts with rigid walls having square-wave wall corrugations is considered in the context of a perturbation formulation. Using the ratio of wall corrugation amplitude to the mean duct half width, a small parameter is defined and a two levels of approximations are obtained. The first-order solution produces an analytical description of the pressure field inside the duct. The second-order solution yields an analytical estimate of the phase speed of waves transmitting through the duct. The effect of wall corrugation density on acoustic impedance and wave speeds is highlighted. The analysis reveals that waves propagating in a duct with square-wave wall corrugation are slower than waves propagating in a duct with sinusoidal wave corrugation having the same corrugation wavelength.
2
Nair, M. N. B., and S. V. Subrahmanyam. "Ultrastructure of the Epithelial Cells and Oleogumresin Secretion in Boswellia Serrata (Burseraceae)." IAWA Journal 19, no. 4 (1998): 415–27. http://dx.doi.org/10.1163/22941932-90000662.
Abstract:
The ultrastructure of epithelial cells of oleo-gumresin ducts in Boswellia serrata, the source of Indian olibanum, is described. Oleo-gumresin ducts are present in primary and secondary phloem. The duct lumen forms an enlarged apoplastic space surrounded by epithelial cells. The epithelial cells are rich in dictyosomes, lipid bodies, mitochondria with dilated cristae, multivesicular bodies, osmiophilic materials, plastids and vesicIes. Plastids have poorly developed internal membranes. Dictyosomes and plastids are possible sites of resin synthesis. The gum component of the exudate is formed in dictyosomes and from the outer layers of the inner tangential wall (wall facing the duct lumen). This wall is replenished from inside by the activity of dictyosomes. The secretory materials are transported to the apoplast by granulocrine and eccrine secretion. They migrate through the loose microfibrils of the inner tangential wall into the duct lumen. Rarely, epithelial cells of young ducts have rudimentary plasmodesmata on the inner tangential wall which may be channels for passage of secretory materials into the duct lumen.
3
Morrison, Janice C., L. Carl Greve, and John M. Labavitch. "The Role of Cell Wall-degrading Enzymes in the Formation of Gum Ducts in Almond Fruit." Journal of the American Society for Horticultural Science 112, no. 2 (March 1987): 367–72. http://dx.doi.org/10.21273/jashs.112.2.367.
Abstract:
Abstract Cell wall-degrading enzymes were extracted from the cell wall free space of mesocarp tissue from immature almonds [Prunus dulcis(Mill.)D.A. Webb, ‘Nonpareil’]. The activities of several of these enzymes were found to correlate with the development of gum ducts in this tissue. Polygalacturonase (EC 3.2.1.15) and 1,3-β-D-glucanase (EC 3.2.1.39) activities rose sharply at, or just prior to, the early schizogenous stage of duct initiation, while increases in α-galactosidase (EC 3.2.1.22), β-galactosidase (EC 3.2.1.23), α-arabinosidase (EC 3.2.1.55), and α-mannosidase (EC 3.2.1.24) activities were correlated with the later lysigenous stage of duct formation. Cell wall analysis of almond mesocarp tissue sampled the week preceding gum duct formation determined that the predominant noncellulosic sugars present in the mesocarp cell walls are arabinose, galactose, xylose, and glucose, with smaller amounts of rhamnose and mannose also present. The walls also contain a high percentage of galacturonic acid and trace amounts of glucuronic acid. Methylation analysis of the cell walls confirmed that many of the specific glycosidic linkages that are cleaved by the enzymes tested are present in the mesocarp cell walls immediately prior to gum duct formation.
4
Mahmoud, Mohammed H., Fouad A. Saleh, and Abeer H. Faleh. "Compound Heat Transfer Enhancement in Dimpled and Sinusoidal Metal Solar Wall Ducts Fitted with Wired Inserts." Journal of Engineering 18, no. 05 (June 19, 2023): 591–610. http://dx.doi.org/10.31026/j.eng.2012.05.05.
Abstract:
An improved Metal Solar Wall (MSW) with integrated thermal energy storage is presented in this research. The proposed MSW makes use of two, combined, enhanced heat transfer methods. One of the methods is characterized by filling the tested ducts with a commercially available copper Wired Inserts (WI), while the other one uses dimpled or sinusoidal shaped duct walls instead of plane walls. Ducts having square or semi-circular cross sectional areas are tested in this work.A developed numerical model for simulating the transported thermal energy in MSW is solved by finite difference method. The model is described by system of three governing energy equations. An experimental test rig has been built and six new duct configurations have been fabricated and tested. Air is passed through the six ducts with Reynolds numbers from 1825 to 7300.Six, new, correlations for Nusselt number and friction factor are developed to assess the benefits that are gained from using the WI and the dimpled and sine-wave duct walls. It is found that higher heat transfer rates are achieved using the Dimpled, semi–circular duct with Wired Inserts (DCWI). Also, it is found that Nusselt number and the pressure drop in the DCWI are respectively(44.2% -100%) and (101.27% - 172.8%) greater than those of the flat duct with WI. The improvement in Nusselt number for flat duct with WI is found to be (1.4 – 2) times the values for flat duct with no WI. The results demonstrated that DCWI provides enhancements efficiency value that is higher than those obtained from other types of ducts. The developed MSW ducts have added to local knowledge a better understanding of the compound heat transfer enhancement.
5
Ahn, SooWhan, and MyungSung Lee. "Heat Transfer Augmentation in a Divergent Duct with Angled Ribs." International Journal of Air-Conditioning and Refrigeration 25, no. 01 (March 2017): 1750008. http://dx.doi.org/10.1142/s2010132517500080.
Abstract:
Heat transfer characteristics in the rectangular divergent duct with parallel angled ribs are experimentally compared with the straight smooth circular duct. The ribs with four different parallel angles ([Formula: see text], 45[Formula: see text], 60[Formula: see text], and 90[Formula: see text]) are glued on the duct’s two opposite walls as well as on the duct’s one sided wall only, respectively. The 0.72[Formula: see text]-inclined walls are installed at the two opposite walls of the rectangular divergent duct. The test section of 1000[Formula: see text]mm long has the cross section of [Formula: see text][Formula: see text]mm2 at inlet and [Formula: see text][Formula: see text]mm2 at exit. The ribbed walls are manufactured with a rib height [Formula: see text][Formula: see text]mm and the ratio of rib spacing ([Formula: see text]) to height([Formula: see text]) [Formula: see text] 10. The main findings are summarized that the increase in the dimensionless Nusselt number for the flow attack angles can be seen in the order of 90[Formula: see text], 30[Formula: see text], 60[Formula: see text], and 45[Formula: see text] at the two opposite ribbed divergent wall ducts, in addition, the average Nusselt number in the divergent rectangular duct with two opposite ribbed walls is somewhat greater than in the ribbed straight cross-sectional rectangular duct.
6
Ashrafizadeh, A., G. D. Raithby, and G. D. Stubley. "Direct Design of Ducts." Journal of Fluids Engineering 125, no. 1 (January 1, 2003): 158–65. http://dx.doi.org/10.1115/1.1514201.
Abstract:
This paper describes a method for calculating the shape of duct that leads to a prescribed pressure distribution on the duct walls. The proposed design method is computationally inexpensive, robust, and a simple extension of existing computational fluid dynamics methods; it permits the duct shape to be directly calculated by including the coordinates that define the shape of the duct wall as dependent variables in the formulation. This “direct design method” is presented by application to two-dimensional ideal flow in ducts. The same method applies to many problems in thermofluids, including the design of boundary shapes for three-dimensional internal and external viscous flows.
7
Mateshuk-Vatseba, L. R., I. I. Hirniak, and U. Y. Pidvalna. "Morphological features of the wall of common bile duct under the conditions of experimental opioid exposure." Reports of Morphology 26, no. 2 (October 12, 2020): 26–31. http://dx.doi.org/10.31393/morphology-journal-2020-26(2)-04.
Abstract:
The morphological condition of the bile ducts remains one of the most important problems of modern medical science. In order to obtain an analgesic effect in patients with acute cholangitis, opioids are often used. However, information on the effectiveness of opioids in the treatment of pathological conditions of the bile ducts is contradictory. The rapidly progressive destruction of the intrahepatic bile ducts associated with the use of narcotic agents has been described. Further study of the effect of opioids on the structural organization of the common bile duct is relevant. In order to establish the morphological state of the common bile duct under conditions of long-term opioid exposure, a study was performed on 24 sexually mature white male rats, aged 3.5-5.0 months and weighing 180-200 g, which were injected intramuscularly with Nalbuphine for 6 weeks. The study material is represented by histological specimens of the common bile duct of white rats. The “Aver Media” computer system was used to photograph microspecimens. The “ImageJ” computer program was used to measure the diameter of the lumen and the wall thickness of the common bile duct. After 2 weeks of Nalbuphine administration to white rats, plethora of wall microvessels and a significant increase in the longitudinal diameter of the lumen of the common bile duct were observed. After 4 weeks of the experiment, the common bile duct was dilated, the transverse and longitudinal diameters of its lumen almost doubled, pathological changes in its wall had all the signs of inflammation. In the later stages of the experiment (introduction of Nalbuphine for 6 weeks), the pathological changes increased and manifested by destructuring the wall of the common bile duct, disorganization of cholangiocytes, thinning of the cell layer due to detachment of cholangiocytes, polymorphism of their nuclei, destruction of intercellular junctions, stratification of its own plate, vacuolar dystrophy of the muscular membrane “varicose” expansion of venules, significant smooth muscle hyperplasia of arterioles, the presence of perivascular lymphocytic infiltrates in the duct wall.
8
Nilsson, Erik, Sylvain Ménard, Delphine Bard Hagberg, and Nikolaos-Georgios Vardaxis. "Acoustical Treatments on Ventilation Ducts through Walls: Experimental Results and Novel Models." Acoustics 4, no. 1 (March 18, 2022): 276–96. http://dx.doi.org/10.3390/acoustics4010017.
Abstract:
Sound reduction is complex to estimate for acoustical treatments on ventilation ducts through walls. Various acoustical treatments are available for ventilation ducts, including internal lining (absorption along the inner perimeter), external lagging (external sound insulation), silencer, and suspended ceilings. Previous studies have examined how silencers and the internal lining affect the sound transmission of ventilation ducts. However, there are few theories to predict the effect of external lagging in combination with ventilation ducts and how the total sound reduction is affected. This article aims to investigate different acoustical treatments and develop theoretical models when external lagging with stone wool is used to reduce flanking sound transmission via the surface area of ventilation ducts. Theoretical models are developed for external lagging and compared with measurement data. Measurements and theory are generally in good agreement over the third-octave band range of 100–5000 Hz. The developed models clarify that the distance closest to the wall has the main impact on sound reduction for a combined system with a wall and a ventilation duct. Suspended ceilings and silencers are found to be enough as acoustical treatments for certain combinations of ventilation ducts and walls. However, external lagging seems to be the only effective solution in offices and schools when a large ventilation duct passes through a wall with high sound reduction.
9
Maloshtan, Oleksandr, Rostyslav Smachilo, Oleksandr Tishchenko, Аndrii Nekludov, Мariia Klosova, and Оleg Volchenko. "THE ROLE OF THE INFECTIOUS FACTOR IN THE DEVELOPMENT OF CHOLANGITIS." JOURNAL OF THE NATIONAL ACADEMY OF MEDICAL SCIENCES OF UKRAINE, Issue 1; 2021 (May 26, 2021): 32–37. http://dx.doi.org/10.37621/jnamsu-2021-1-4.
Abstract:
Introduction. The problems of the pathogenesis of cholangitis have not been finally clarified to date. Aim: to investigate the dynamics of microbial contamination of the biliary tract in obstructive jaundice before and after decompression. Materials and methods. To determine the significance of the infectious factor in the development of acute cholangitis, bile from the common bile duct was examined in 40 patients with the biliary tract obstruction, which were divided into three groups according to the clinical course of the disease. Results. The quantitative infection indicators of the common bile duct were studied in asymptomatic choledocholithiasis, in obstructive jaundice without clinical manifestations of cholangitis and in a developed clinic of cholangitis. It has been proven that endoscopic decompression of the biliary tree allows to obtain an almost instant therapeutic effect, the number of colony-forming units of the pathogen decreases by almost three orders of magnitude within 3 days. However, in phlegmonous inflammation of the bile duct wall patients, this period was significantly lengthened, and the course of the disease, according to the Tokyo Guidelines (2013), was assessed as severe. Conclusion. In the study of quantitative infection indicators in patients with a bright clinic of cholangitis, a significant decrease in the number of colony-forming units was observed already on the third day after endoscopic papilosphincterotomy due to an adequate drainage effect. When a stone is driven into the large papilla of the duodenum, the common bile duct turns into an analogue of an abscess. Opening the papilla not only frees the mouth of the duct from the stone, but also provides free passage of the contents of the common bile duct (pus) into the duodenum. This provides an almost instant healing effect. When comparing the severity of cholangitis with the histological picture of the wall of the bile ducts (common bile duct, intrahepatic ducts), data were obtained that it is in patients with a severe form of the disease that phlegmonous inflammation of the wall of the duct system takes place. When comparing the severity of cholangitis with the histological picture of the wall of the bile ducts (common bile duct, intrahepatic ducts), data were obtained that phlegmonous inflammation of the wall of the duct system is observed precisely in patients with a severe form of the disease. Keywords: cholangitis, endoscopic decompression
10
Subrahmanyam, S. V., and J. J. Shah. "The Metabolic Status of Traumatic Gum Ducts in Moringa Oleifera Lam." IAWA Journal 9, no. 2 (1988): 187–95. http://dx.doi.org/10.1163/22941932-90001067.
Abstract:
Traumatic gum ducts develop lysigenously in the bark of Moringa oleifera Lam. as a result of injury. The phloem parenchyma cells at the locus of gum duct formation enlarge and are enriched with cytoplasm and nucleoplasm. These duct initials show higher succinic dehydrogenase (SDH) and acid phosphatase (ACPase) activities compared to the neighbouring cells. The duct initials undergo autolysis to form the duct lumen. The epithelial cells of a gum duct have various shapes and show intense staining for nucleic acids, proteins and insoluble polysaccharides as compared to the neighbouring cells. The epithelial cells are also rich in enzymes viz. SDH, ACPase and lipase. Epithelial cells show labyrinthine wall deposition. These deposits are more towards the duct lumen side than the radial wall side. The inner tangential wall of the epithelial cells facing the duct lumen appears swollen. The degenerating epithelial cells show diffuse reaction products of SDH and ACPase. Some epithelial cells accumulate phenolics and by autolysis of such cells their phenolic contents are released into the gum duct.
11
Zhang, Y. M., W. Z. Gu, and J. C. Han. "Heat Transfer and Friction in Rectangular Channels With Ribbed or Ribbed-Grooved Walls." Journal of Heat Transfer 116, no. 1 (February 1, 1994): 58–65. http://dx.doi.org/10.1115/1.2910884.
Abstract:
The effect of compound turbulators on friction factors and heat transfer coefficients in rectangular channels with two opposite ribbed-grooved walls was determined for a Reynolds number range of 10,000 to 50,000. The channel width-to-height ratio was 10. The fully developed heat transfer coefficients and friction factors on the ribbed-grooved and smooth side walls of each test channel were measured for six rib-groove spacings (p/e = 8, 10, 15, 20, 25, and 30). The fully developed friction and heat transfer in similar aspect ratio rectangular channels with two opposite ribbed walls with two rib spacings (p/e = 8.5 and 11.5) was also measured for comparison. The results show that the heat transfer performance of the rib-groove roughened duct is much better than the rib roughened duct. The rib-groove roughened wall enhances the heat transfer 3.4 times and pays 6 times the pressure drop penalty, whereas the rib roughened wall, with similar rib height and rib spacing, enhances the heat transfer 2.4 times and pays about the same pressure drop penalty. Semi-empirical friction and heat transfer correlations were obtained. Flow measurements show that the roughened ducts have flatter velocity profiles than the smooth duct and rib-groove roughened duct produces higher turbulence intensity than the rib roughened duct. The flatter velocity profile and higher turbulence intensity are responsible for producing higher heat transfer.
12
Vaisakh, S., and TM Muruganandam. "Influence of multi-wall separation control on normal-shock-induced separation in supersonic duct flows." Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering 233, no. 9 (August 14, 2018): 3184–92. http://dx.doi.org/10.1177/0954410018793789.
Abstract:
In this work, separation due to the interaction of normal shock with wall boundary layers in a supersonic duct flow is studied using schlieren, oil flow visualization, and pressure measurements. This study uses separation control devices on three walls of a rectangular duct and investigates the influence of adding control on one wall and on the other walls. It was found that control on any wall has effect on separation on other walls. This effect was found to be due to the change in the size of corner separations. Pressure recovery was found to be steeper with the introduction of more control devices in the duct.
13
Ingham, D. B., D. J. Keen, and P. J. Heggs. "Flows in Vertical Channels With Asymmetric Wall Temperatures and Including Situations Where Reverse Flows Occur." Journal of Heat Transfer 110, no. 4a (November 1, 1988): 910–17. http://dx.doi.org/10.1115/1.3250592.
Abstract:
Numerical investigations are conducted into steady laminar combined convection flows in vertical parallel plate ducts with asymmetric constant wall temperature boundary conditions. The streamwise diffusion terms in the governing equations are neglected and the resulting parabolic equations are expressed in an implicit finite difference scheme and solved using a marching technique. In certain situations the combination of the size of the ratio |Gr/Re| and the difference in temperature between the walls of the duct is such that the fully developed flow profile, as the streamwise coordinate tends toward infinity, includes reverse flow in the vicinity of the cold wall. Techniques first used in a previous study are employed in finding a solution through the whole domain of the fluid for those situations involving reverse flow in the fully developed region. Comparisons with existing data near the duct entrance and far along the duct show very good agreement.
14
Conceição, Eusébio, Mª Inês Conceição, Mª Manuela Lúcio, João Gomes, and Hazim Awbi. "Case study of a multiple confluents jets system in a virtual chamber." E3S Web of Conferences 356 (2022): 01011. http://dx.doi.org/10.1051/e3sconf/202235601011.
Abstract:
This article presents a case study of a multiple confluents jets system in a virtual chamber. In this study, it is obtained the behavior of the airflow in an office, simulated by a virtual camera, whose ventilation system is of the horizontal confluent jets type. The ventilation system has an inlet system consisting of four vertical ducts mounted in the corners of the compartment. Each duct has four groups of 32 nozzles, aligned and equally spaced, positioned from the base of the duct close to the floor. Each two groups of nozzles are directed towards each of the walls adjacent to the duct The exhaust system consists of a quadrangular vertical duct mounted close to the ceiling and positioned in the center of the compartment. The study uses a numerical differential model in order to simulate the Computational Fluids Dynamics. Ventilation by horizontal confluent jets creates a horizontal air velocity close to the wall surface as well as the floor surface. With the increase in the exit velocity of the jets, the interactive effect of the confluence of the jets, coming from opposite ducts, in the central area of the wall becomes more evident. The airflow resulting from the interactions of the jets has an upward characteristic towards the exhaust system.
15
Ortloff, Charles R. "Supercritical Froude Number Flow through Ducts with Statistically Roughened Walls." Water 15, no. 15 (August 7, 2023): 2849. http://dx.doi.org/10.3390/w15152849.
Abstract:
High-speed fluid flows over roughened surfaces occur in many engineering applications; one important application involves high velocity water flows in pipelines with roughened interior walls where the wall roughness affects head loss estimates necessary for engineering design purposes. The present analysis provides an analytical solution of the fluid physics underlying the induced static pressure profile resulting from high Froude number supercritical velocity through duct with random wall roughness. The analytic solution of the hyperbolic governing small perturbation velocity potential equation subject to high Froude number flows brings forward characteristic wave solutions that determine the static pressure profile in a duct with random height wall roughness. While current engineering practice utilizes semi-empirical engineering equations employing test data to determine the friction factor, velocity and static pressure profiles and head loss for different roughness types in different sized ducts as a function of Reynolds number (as summarized in a later section of the paper), the present analysis provides a new analytical method to determine the fluid physics involved in the static pressure change induced by wall random roughness in ducts subject to high Froude number supercritical flows.
16
Lilly, Jerry, and Jerry Lilly. "Breakout from HVAC ductwork." INTER-NOISE and NOISE-CON Congress and Conference Proceedings 264, no. 1 (June 24, 2022): 683–94. http://dx.doi.org/10.3397/nc-2022-799.
Abstract:
Noise radiated by HVAC ductwork is becoming more important with the recent trend to eliminate ceilings in many office buildings. The ASHRAE Applications Handbook has provided a method for calculating breakout from ductwork since 1987. This method requires determining the duct wall transmission loss, which is not the same at the conventional transmission loss obtained using ASTM E90 because of the shape of the duct wall and because the sound field inside the duct is not random incidence. This methodology assumes that the sound level inside the duct is the same throughout the entire duct length, which is only approximately true for short, unlined ducts, but not always the case. In 2003 the ASHRAE Handbook presented a revised duct breakout calculation method that takes into consideration the sound attenuation with distance inside the duct, assuming that the sound level decreases at a constant rate. The results of a 2017 ASHRAE research project studying the insertion loss versus length of acoustically lined ducts revealed that the attenuation rate is not constant with length. This paper demonstrates the difference between the various breakout calculation methods and highlights the importance of including the attenuation rate in the analysis.
17
Suzumura, Kazuhiro, Etsuro Hatano, Masaharu Tada, Hideaki Sueoka, Hiroshi Nishida, Kenjiro Iida, Seikan Hai, et al. "Difficulty Achieving a Preoperative Diagnosis of IgG4-Related Sclerosing Cholangitis." Case Reports in Gastroenterology 12, no. 2 (August 21, 2018): 425–31. http://dx.doi.org/10.1159/000490523.
Abstract:
A 75-year-old male was admitted to our hospital because of bile duct stenosis. He had no medical history of autoimmune disease. The level of tumor markers, serum IgG, and IgG4 were within normal ranges. Computed tomography showed perihilar and distal bile duct stenosis and wall thickening without swelling or abnormal enhancement of the pancreas. Endoscopic retrograde cholangiopancreatography showed perihilar and distal bile duct stenosis. A biopsy and cytology from the distal bile duct stenosis suggested adenocarcinoma, and cytology from the perihilar bile duct also suggested adenocarcinoma. A preoperative diagnosis of perihilar and distal bile duct cancer was made, and the patient underwent left hepatectomy and pancreaticoduodenectomy. Resected specimens showed wall thickening in the perihilar and distal bile duct; however, tumors were unclear. A histopathological examination revealed lymphoplasmacytic infiltration, storiform fibrosis, and obliterative phlebitis in the perihilar and distal bile ducts. Immunohistochemistry revealed diffuse infiltration of IgG4-positive plasma cells in the perihilar and distal bile ducts. Lymphoplasmacytic infiltration, inflammatory change, storiform fibrosis, and obliterative phlebitis were shown in the pancreas. A final diagnosis of IgG4-related sclerosing cholangitis (IgG4-SC) with autoimmune pancreatitis was made. We herein report a case in which a preoperative diagnosis of IgG4-SC was difficult due to normal serum IgG4 levels and no obvious pancreatic lesion.
18
MÖHRING, WILLI. "Energy conservation, time-reversal invariance and reciprocity in ducts with flow." Journal of Fluid Mechanics 431 (March 25, 2001): 223–37. http://dx.doi.org/10.1017/s0022112000003050.
Abstract:
A sound wave propagating in an inhomogeneous duct consisting of two semi-infinite uniform ducts with a smooth transition region in between and which carries a steady flow is considered. The duct walls may be rigid or compliant. For an irrotational sound wave it is shown that the three properties of the title are closely related, such that the validity of any two implies the validity of the third. Furthermore it is shown that the three properties are fulfilled for lossless locally reacting duct walls provided the impedance varies at most continuously. For piecewise-continuous wall properties edge conditions are essential. By an analytic continuation argument it is shown that reciprocity remains true for walls with loss. For rotational flow, energy conservation theorems have been derived only with the help of additional potential-like variables. The inter-relation between the three properties remains valid if one considers these additional variables to be known. If only the basic gasdynamic variables in both half-ducts are known, one cannot formulate an energy conservation equation; however, reciprocity is fulfilled.
19
Zhou, Jun Wei, Da Zheng Wang, and Ya Nan Li. "Optimization and Flow Analysis of Ducted Tidal Stream Turbine." Advanced Materials Research 694-697 (May 2013): 683–88. http://dx.doi.org/10.4028/www.scientific.net/amr.694-697.683.
Abstract:
Efficiency of the tidal stream turbine with thin-wall axisymmetric ducts was numerically simulated. The ducts design parameters of diffuser curves, expansion ratio and duct length were simply optimized. The results showed that the duct of second order diffuser curve, expansion ratio of 2.25 and a length-diameter ratio of 1.2 has the best performance. By comparison of different ducts flow, it revealed that flow separation at the duct outlet and the ejection influenced ducted turbine efficiency. The separation caused blockage and flow rate decreasing, and so performance deteriorated. The ejection caused lower pressure at the outlet of the duct, which allowed higher pressure drop through turbine impeller, and so improved turbine efficiency.
20
Molokov, S., and L. Bühler. "Liquid metal flow in a U-bend in a strong uniform magnetic field." Journal of Fluid Mechanics 267 (May 25, 1994): 325–52. http://dx.doi.org/10.1017/s0022112094001205.
Abstract:
Magnetohydrodynamic flows in a U-bend and in a right-angle bend are considered with reference to the toroidal concepts of self-cooled liquid-metal blankets. The ducts composing the bends have rectangular cross-sections. The applied magnetic field is aligned with the toroidal duct and perpendicular to ducts supplying liquid metal. For high Hartmann numbers the flow region is divided into cores and boundary layers of different types. The magnetohydrodynamic equations are reduced to a system of partial differential equations governing wall electric potentials and the core pressure. The system is solved numerically. The results show that the flow is very sensitive to variations of certain parameters, such as the wall conductance ratio and the aspect ratio of the toroidal duct cross-section. Depending on these parameters, the flow exhibits a variety of qualitatively different flow patterns. In particular, structures of helical and vortex type are obtained. A high-velocity jet occurs at the plasma-facing first wall and there is mixing of the fluid in the toroidal duct. These factors lead to desirable heat-transfer conditions.
21
Hirota, M., H. Fujita, and H. Yokosawa. "Experimental Study on Convective Heat Transfer for Turbulent Flow in a Square Duct With a Ribbed Rough Wall (Characteristics of Mean Temperature Field)." Journal of Heat Transfer 116, no. 2 (May 1, 1994): 332–40. http://dx.doi.org/10.1115/1.2911405.
Abstract:
This paper presents experimental results concerning a time-mean temperature field obtained in forced convection heat transfer for a turbulent flow through a square duct with a ribbed rough bottom wall. The secondary flow pattern in the duct is reflected in the distribution of the local Nusselt number, the values of which on the smooth walls of the rough duct are 1.71~1.97 times those of the smooth duct. In the upper half cross section near the upper smooth wall opposite the bottom ribbed rough wall, the profile of the mean temperature distribution is similar to that of the primary flow velocity distribution, and the validity of the temperature inner law was confirmed. However, in the lower half cross section near the bottom ribbed rough wall, the dissimilarity between the mean velocity and the mean temperature fields becomes pronounced, and the inner law is not valid for mean temperature distributions. The mechanism of the heat transfer near the ribbed rough wall was examined based on the transport equations of turbulent shear stress and turbulent heat flux.
22
Dorsaf, Beltaifa, Slama Sana Ben, Guebsi Sofiene, Atallah Aziz, Arfa Nafaa, Lahmar Ahlem, and Bacha Dhouha. "A case of hepatic intraductal papillary neoplasm of the bile duct." Archives of Case Reports 7, no. 1 (March 21, 2023): 007–11. http://dx.doi.org/10.29328/journal.acr.1001067.
Abstract:
Introduction: Intraductal Papillary Neoplasm of the Bile ducts (IPNB) is a rare entity characterized by exophytic growth of the bile ducts. Case presentation: In this report, we present a 57-year-old male with no prior medical history consulted for upper right abdominal pain, jaundice and pruritus. Abdominal Ultrasound (US) and magnetic resonance imaging/Bili-magnetic resonance were performed. They revealed that the circumferential parietal thickening of the common hepatic duct had extended approximately 4 cm with moderate dilatation of the left intrahepatic bile ducts. Computed tomography showed no evidence of distant metastasis. Biopsy revealed a high-grade intraductal papillary neoplasm. After 40 days, the patient had left hepatectomy with resection of the main bile duct and the gallbladder. Macroscopic examination of the surgical specimen showed a dilatation duct at the hilum with thickening of their walls. The histopathology report revealed multiple intra-hepatic papillary neoplasms with high-grade dysplasia with an invasive carcinoma component in the left hepatic duct without extending to the biliary wall, classified as pT1N0. Conclusion: This premalignant lesion has the potential to transform into invasive carcinoma if not properly diagnosed. Our case illustrates how early identification can lead to potential surgical resection.
23
Salameh, Tareq, and Bengt Sunden. "A numerical investigation of heat transfer in a smooth bend part of a U-duct." International Journal of Numerical Methods for Heat & Fluid Flow 24, no. 1 (December 20, 2013): 137–47. http://dx.doi.org/10.1108/hff-03-2012-0066.
Abstract:
Purpose – The aim of this paper is to study two-dimensional numerical simulations of the flow and temperature fields inside the bend (turn) part of a U-duct. Design/methodology/approach – Several turbulence models based on two and five equations were used to solve the momentum and energy equations inside the bend (turn) part of the U-duct. For two-equation models, both the renormalization group and realizable k-ɛ turbulence models were implemented. The five-equation model used is a Reynolds stress model with different wall boundary conditions. Standard, non-equilibrium and enhanced wall functions were used in parallel with the two- and five-equation models to treat the turbulent flow near the duct walls. Findings – Several turbulence models were used to simulate the flow and temperature fields along the bend part of a U-duct with different inlet and thermal boundary conditions. The numerical results indicate that the renormalization and realizable k-ɛ turbulence models with standard wall function treatment gave the best results when compared with experimental data obtained for similar conditions. Research limitations/implications – For heat transfer analysis, two different thermal boundary conditions, i.e. constant wall temperature and constant heat flux at the wall are implemented. The results are calculated for Reynolds number equal 20,000. Practical implications – The results can be used in designing heat exchangers, piping and duct systems, and internal passage cooling of gas turbine blades. Originality/value – The numerical results obtained here concentrate on the detailed investigation of flow and temperature field at the outer wall of the bend part. Different boundary conditions at the inlet and the outer bend walls of the U-duct were applied to study how these boundary conditions affect the flow and temperature fields.
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Samanta, A., R. Vinuesa, I. Lashgari, P. Schlatter, and L. Brandt. "Enhanced secondary motion of the turbulent flow through a porous square duct." Journal of Fluid Mechanics 784 (November 6, 2015): 681–93. http://dx.doi.org/10.1017/jfm.2015.623.
Abstract:
Direct numerical simulations of the fully developed turbulent flow through a porous square duct are performed to study the effect of the permeable wall on the secondary cross-stream flow. The volume-averaged Navier–Stokes equations are used to describe the flow in the porous phase, a packed bed with porosity ${\it\varepsilon}_{c}=0.95$. The porous square duct is computed at $\mathit{Re}_{b}\simeq 5000$ and compared with the numerical simulations of a turbulent duct with four solid walls. The two boundary layers on the top wall and porous interface merge close to the centre of the duct, as opposed to the channel, because the sidewall boundary layers inhibit the growth of the shear layer over the porous interface. The most relevant feature in the porous duct is the enhanced magnitude of the secondary flow, which exceeds that of a regular duct by a factor of four. This is related to the increased vertical velocity, and the different interaction between the ejections from the sidewalls and the porous medium. We also report a significant decrease in the streamwise turbulence intensity over the porous wall of the duct (which is also observed in a porous channel), and the appearance of short spanwise rollers in the buffer layer, replacing the streaky structures of wall-bounded turbulence. These spanwise rollers most probably result from a Kelvin–Helmholtz type of instability, and their width is limited by the presence of the sidewalls.
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Teleszewski, Tomasz Janusz, and Slawomir Adam Sorko. "Effect of viscous dissipation on forced convection for laminar flow through a straight regular polygonal duct using BEM method." International Journal of Numerical Methods for Heat & Fluid Flow 28, no. 1 (January 2, 2018): 220–38. http://dx.doi.org/10.1108/hff-09-2017-0371.
Abstract:
Purpose The purpose of this paper is to investigate the effect of the viscous dissipation of laminar flow through a straight regular polygonal duct on forced convection with constant axial wall heat flux with constant peripheral wall temperature using the boundary element method (BEM). Design/methodology/approach Both the wall heating case and the wall cooling case are considered. Applying the velocity profile obtained for the duct laminar flow and the energy equation with the viscous dissipation term is solved exactly for the constant wall heat flux using the BEM. The numerical values are obtained by means of a computer program, written by the authors in Fortran. The results of the BEM approach are verified by analytic models. Nusselt numbers are obtained for flows with a different number of sides of a regular polygonal duct and Brinkman numbers. Findings When the difference in temperature between the wall temperature and the fluid bulk temperature changes the sign, then the functions of the Nusselt number with the Brinkman number generated some singularities (BrqLs). For the Brinkman number referring to the total wall linear power, with the increasing value of the number of sides of a regular polygonal duct, BrqLs decreases in the range of 3 ≤ n < ∞. If the BrqL < BrqLs, it is possible to note that, in general, the Nusselt number is higher for cross-sections having a lower value of the number of sides of a regular polygonal duct. For BrqL > BrqLs, this rule is reversed. Originality/value This paper illustrates the effects of viscous dissipation on laminar forced convective flow in regular polygon ducts with a different number n of sides. A compact relationship for the Nusselt number vs the Brinkman number referring to the temperature difference between the wall temperature and the fluid bulk temperature and the Brinkman number, which is based on the total wall linear power, have been proposed.
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Li and, A., and B. F. Armaly. "Laminar Mixed Convection Adjacent to Three-Dimensional Backward-Facing Step." Journal of Heat Transfer 124, no. 1 (October 5, 2001): 209–13. http://dx.doi.org/10.1115/1.1423909.
Abstract:
Simulations of three-dimensional laminar buoyancy-assisting mixed convection adjacent to a backward-facing step in a vertical rectangular duct are presented to demonstrate the influence of Grashof number on the distributions of the Nusselt number, and the reverse flow regions that develop adjacent to the duct’s walls. The Reynolds number, and duct’s geometry are kept constant: heat flux at the wall downstream from the step is kept uniform but its magnitude varied to cover a Grashof number range of 0–4000; all the other walls in the duct are kept at adiabatic condition; and the flow, upstream of the step, is treated as fully developed and isothermal. Increasing the Grashof number results in increasing the Nusselt number; the size of the secondary recirculation flow region adjacent to the stepped wall; the size of the reverse flow region adjacent to the sidewall and the flat wall; and the spanwise flow from the sidewall toward the center of the duct. On the other hand, the size of the primary recirculation flow region adjacent to the stepped wall decreases and detaches partially from the heated stepped wall as the Grashof number increases. Details are presented and discussed.
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WANG, CHENGPENG, XUANG TIAN, and KEMING CHENG. "NUMERICAL INVESTIGATIONS OF PSEUDO-SHOCK WAVES IN VARIABLE CROSS-SECTION DUCTS." Modern Physics Letters B 23, no. 03 (January 30, 2009): 485–88. http://dx.doi.org/10.1142/s0217984909018710.
Abstract:
The Pseudo-Shock Wave (PSW), which appears when supersonic flow in duct decelerates to subsonic, is a complicated process due to the interaction between boundary layer and shock wave. It significantly affects the performance and efficiency of flow devices. In this paper, PSW in two kinds of variable cross-section ducts, edge-varied and corner-varied, was investigated through CFD numerical simulation. Compared to the rectangular duct, a shorter and wider separation region is appeared in the corner of the edge-varied duct while the strongest separation is laterally propagated across the entire plane of the corner-varied duct's side wall. This makes the performances of varied ducts different from traditional constant cross-section ducts.
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Saha, Arun K., and Sumanta Acharya. "Turbulent Heat Transfer in Ribbed Coolant Passages of Different Aspect Ratios: Parametric Effects." Journal of Heat Transfer 129, no. 4 (June 8, 2006): 449–63. http://dx.doi.org/10.1115/1.2709653.
Abstract:
Turbulent flow and heat transfer in rotating ribbed ducts of different aspect ratios (AR) are studied numerically using an unsteady Reynolds averaged Navier–Stokes procedure. Results for three ARs (1:1, 1:4, and 4:1) and staggered ribs with constant pitch (P∕e=10) in the periodically developed region are presented and compared. To achieve periodic flow behavior in successive inter-rib modules calculations are performed in a computational domain that extends to two or three inter-rib modules. The computations are carried out for an extended parameter set with a Reynolds number range of 25,000–150,000, density ratio range of 0–0.5, and rotation number range of 0–0.50. Under rotational conditions, the highest heat transfer along the leading and side walls are obtained with the 4:1 AR, while the 1:4 AR has the highest trailing wall Nu ratio and the lowest leading wall Nu ratio. The 1:4 AR duct shows flow reversal near the leading wall (leading to low Nu) at high rotation numbers and density ratios. For certain critical parameter values (low Re, high Ro, and/or DR), the leading wall flow is expected to become nearly stagnant, due to the action of centrifugal buoyancy, leading to conduction-limited heat transfer. The 4:1 AR duct shows evidence of multiple rolls in the secondary flow that direct the core flow to both the leading and trailing surfaces which reduces the difference between the leading and trailing wall heat transfer relative to the other two AR ducts.
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VÁZQUEZ, M. SALINAS, and O. MÉTAIS. "Large-eddy simulation of the turbulent flow through a heated square duct." Journal of Fluid Mechanics 453 (February 25, 2002): 201–38. http://dx.doi.org/10.1017/s0022112001006887.
Abstract:
Large-eddy simulations of a compressible turbulent square duct flow at low Mach number are described. First, we consider the isothermal case with all the walls at the same temperature: good agreement with previous incompressible DNS and LES results is obtained both for the statistical quantities and for the turbulent structures. A heated duct with a higher temperature prescribed at one wall is then considered and the intensity of the heating is varied widely. The increase of the viscosity with temperature in the vicinity of the heated wall turns out to play a major rôle. We observe an amplification of the near-wall secondary flows, a decrease of the turbulent fluctuations in the near-wall region and, conversely, their enhancement in the outer wall region. The increase of the viscous thickness with heating implies a significant augmentation of the size of the characteristic flow structures such as the low- and high-speed streaks, the ejections and the quasi-longitudinal vorticity structures. For strong enough heating, the size limitation imposed by the lateral walls leads to a single low-speed streak located near the duct central plane surrounded by two high-speed streaks on both sides. Violent ejections of slow and hot fluid from the heated wall are observed, linked with the central low-speed streak. A selective statistical sampling of the most violent ejection events reveals that the entrainment of cold fluid, originated from the duct core, at the base of the ejection and its subsequent expansion amplifies the ejection intensity.
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Maloshtan, O. V., A. O. Nekliudov, R. M. Smachylo, A. M. Tyschenko, М. О. Кlyosova, and O. V. Volchenko. "PATHOMORPHOLOGICAL CHANGES IN STRUCTURE OF INTRAHEPATIC DUCTS AND CHOLEDOCH IN PATIENTS WITH ACUTE AND CHRONIC CHOLANGITIS." Kharkiv Surgical School, no. 1 (February 20, 2020): 72–76. http://dx.doi.org/10.37699/2308-7005.1.2020.09.
Abstract:
Summary. Aim. To determine the morphological state of bile duct wall cells in patients with acute and chronic cholangitis at different times after removal of bile hypertension.
Materials and methods. During laparotomy surgery, a bile duct wall biopsy was performed in 48 patients with cholangitis, conditionally divided into 4 groups depending on the period of removal of biliary hypertension: up to 5 days, 12-14 days, 28-30 days and 10-12 months. The control group included 12 patients with choledocholithiasis without clinical signs of cholangitis.
Results and its discussion. Acute cholestasis was recorded in the intrahepatic bile ducts, the expression of which occurred in the first 2 weeks. In the period of 28-30 days, residual effects of acute cholangitis and proliferation of connective tissue both in the walls of the ducts and around them were recorded. In the bile duct wall of patients with cholangitis, the largest changes were recorded within 3-5 days from the beginning of decompression in the form of edematous-desquamative and necrotic phenomena on the part of the epithelium. On the 12-14th day, “attenuation” and demarcation of the inflammatory process were noted, and on the 28-30th day – the development of connective tissue. In patients with long-term (6-12 months) chronic cholangitis, the phenomena of cholestasis, cholangiosclerosis and biliary cirrhosis of the liver were documented, which were not subjected to regression.
Conclusions. The most pleasant for reconstructive interventions after the elimination of cholangitis and biliary hypertension is a period of 3-6 weeks. With prolonged cholangitis, the phenomena of sclerosis and cirrhosis are not regressed.
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Polanczyk, Andrzej, Aleksandra Piechota-Polanczyk, Ludomir Stefanczyk, and Michal Strzelecki. "Shape and Enhancement Analysis as a Useful Tool for the Presentation of Blood Hemodynamic Properties in the Area of Aortic Dissection." Journal of Clinical Medicine 9, no. 5 (May 2, 2020): 1330. http://dx.doi.org/10.3390/jcm9051330.
Abstract:
The aim of this study was to create a mathematical approach for blood hemodynamic description with the use of brightness analysis. Medical data was collected from three male patients aged from 45 to 65 years with acute type IIIb aortic dissection that started proximal to the left subclavian artery and involved the renal arteries. For the recognition of wall dissection areas Digital Imaging and Communications in Medicine (DICOM) data were applied. The distance from descending aorta to the diaphragm was analyzed. Each time Feret (DF) and Hydraulic (DHy) diameter were calculated. Moreover, an average brightness (BAV) was analyzed. Finally, to describe blood hemodynamic in the area of aortic wall dissection, mathematical function combining difference in brightness value and diameter for each computed tomography (CT) scan was calculated. The results indicated that DF described common duct more accurately compare to DHy. While, DHy described more accurately true and false ducts. Each time when connection of true and false duct appeared, true duct had lower brightness compare to common duct and false duct. Moreover, false duct characterized with higher brightness compare to common duct. In summary, the proposed algorithm mimics changes in brightness value for patients with acute type IIIb aortic dissection.
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Kariminia, Atefeh, Mahdi Nili-Ahmadabadi, and Kyung Chun Kim. "Full Three-Dimensional Inverse Design Method for S-Ducts Using a New Dimensionless Flow Parameter." Applied Sciences 11, no. 3 (January 26, 2021): 1119. http://dx.doi.org/10.3390/app11031119.
Abstract:
In this study, a new inverse design method is proposed for the full 3-D inverse design of S-ducts using curvature-based dimensionless pressure distribution as a target function. The wall pressure distribution in a 3-D curved duct is a function of the centerline curvature and the cross-sectional profile and area. A dimensionless pressure parameter was obtained as a function of the duct curvature and height of the cross-sections based on the normal pressure gradient equation. The dimensionless pressure parameter was used to eliminate the effect of the cross-sectional area on the wall pressure distribution. Full 3-D inverse design of an S-shaped duct was carried out by substituting the 3-D duct with a large number of 2-D planar ducts. The ball-spine inverse design method with vertical spins was coupled with the dimensionless pressure parameter as a target function for the design of the planar ducts. The inverse design process was performed in two steps. First, the height of each cross-section was considered constant, and only the duct centerline was allowed to be deformed by applying the difference between the dimensionless pressure on the upper and lower lines of symmetry plane. Then, a constant curvature was considered for each centerline in the equation, and the difference between the current and the target dimensionless pressure was applied to each upper and lower line of the planar sections to correct the heights of the 2-D planar sections, separately. The method was validated by choosing a straight duct as an initial guess, which converges to the target S-shaped duct. The results showed that the method is an efficient physical-based residual-correction method with low computational cost and good convergence rate. The 3-D wall pressure distribution of a high-deflected 3-D S-shaped diffuser was modified to eliminate the separation, secondary flow, and outlet distortion. Finally, the geometry corresponding to the modified pressure was obtained by the proposed 3-D inverse design method, which revealed higher pressure recovery, lower total pressure loss, and lower outlet flow distortion and swirl angle.
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Hwang, J. J., and C. S. Cheng. "Augmented Heat Transfer in a Triangular Duct by Using Multiple Swirling Jets." Journal of Heat Transfer 121, no. 3 (August 1, 1999): 683–90. http://dx.doi.org/10.1115/1.2826033.
Abstract:
Measurements of detailed heat transfer coefficients on two principal walls of a triangular duct with a swirling flow are undertaken by using a transient liquid crystal technique. The vertex corners of the triangular duct are 45, 45, and 90 deg. The swirl-motioned airflow is induced by an array of tangential jets on the side entries. The effects of flow Reynolds number (8600 ≦ Re ≦ 21000) and the jet inlet angle (α = 75, 45, and 30 deg) are examined. Flow visualization by using smoke injection is conducted for better understanding the complicated flow phenomena in the swirling-flow channel. Results show that the heat transfer for α = 75 deg is enhanced mainly by the wall jets as well as the impinging jets; while the mechanisms of heat transfer enhancement for α = 45 and 30 deg could be characterized as the swirling-flow cooling. On the bottom wall, jets at α = 75 deg produce the best wall-averaged heat transfer due to the strongest wall-jet effect among the three angles (α) investigated. On the target wall, however, the heat transfer enhancements by swirling flow (α = 45 and 30 deg) are slightly higher than those by impinging jets (α = 75 deg). Correlations for wall-averaged Nusselt number for the bottom and target walls of the triangular duct are developed in terms of the flow Reynolds number for different jet inlet angles.
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RIENSTRA, S. W. "Sound transmission in slowly varying circular and annular lined ducts with flow." Journal of Fluid Mechanics 380 (February 10, 1999): 279–96. http://dx.doi.org/10.1017/s0022112098003607.
Abstract:
Sound transmission through straight circular ducts with a uniform inviscid mean flow and a constant acoustic lining (impedance wall) is classically described by a modal expansion. A natural extension for ducts with axially slowly varying properties (diameter and mean flow, wall impedance) is a multiple-scales solution. It is shown in the present paper that a consistent approximation of boundary condition and isentropic mean flow allows the multiple-scales problem to have an exact solution. Since the calculational complexities are no greater than for the classical straight duct model, the present solution provides an attractive alternative to a full numerical solution if diameter variation is relevant. A unique feature of the present solution is that it provides a systematic approximation to the hollow-to-annular cylinder transition problem in the turbofan engine inlet duct.
35
Levine, Steven B., Lee D. Rowe, William M. Keane, and Joseph P. Atkins. "Evaluation and Treatment of Frontal Sinus Fractures." Otolaryngology–Head and Neck Surgery 95, no. 1 (July 1986): 19–22. http://dx.doi.org/10.1177/019459988609500105.
Abstract:
We treated twenty-three patients with blunt or penetrating wounds of the frontal sinus from 1978 through 1983. Nondisplaced anterior wall fractures were observed or explored. Posterior table fractures—with displacement confirmed by computed tomography or polycycloidal tomography—were explored. Either obliteration of the sinus or nasofrontal duct reconstruction with a Sewall-Boyden-McKnaught flap was selected, depending on the magnitude of duct injury. In all cases, the anterior wall was primarily reconstructed. All penetrating wounds with posterior table involvement were treated by cranialization of the frontal sinus and temporalis muscle obliteration of the nasofrontal ducts. Only one case of meningitis occurred, resulting in prolonged hospitalization.
36
Cwikiel, W., J. Harnek, E. Zoucas, and U. Stenram. "Electrolytic stent in the normal bile duct." Acta Radiologica 39, no. 2 (March 1998): 157–60. http://dx.doi.org/10.1080/02841859809172170.
Abstract:
Purpose: to evaluate and compare changes in the bile-duct wall after the insertion of electrolytic and nonelectrolytic stents Material and Methods: the electrolytic stents were composed of 3 different layers (iron, isolating polyethylene and tantalum) and were implanted surgically in the bile duct of 8 healthy pigs. the nonelectrolytic stents were also composed of 3 layers (2 layers of tantalum and an isolating layer of polyethylene) and were implanted surgically in the bile ducts of 9 healthy pigs. After an observation time of 8 weeks, the pigs were killed and the bile ducts were excised and sent for histopathological examination Results: One pig was killed after the procedure owing to postoperative complications; all the other pigs survived without complications. Migration of the stent to the bowel occurred in 4 pigs. A slight inflammatory reaction was seen at histopathological examination in 6 pigs with the electrolytic stent and in 6 pigs with the nonelectrolytic stent. There was no difference in the specimens from pigs with electrolytic and nonelectrolytic stents Conclusion: the electrolytic stents did not cause more changes in the normal bile-duct wall than the nonelectrolytic stents
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Kafle, Akinchan, Bidur Adhikari, Rajani Shrestha, and Nirju Ranjit. "Anatomic Variations of the Right Hepatic Duct: Results and Surgical Implications From a Cadaveric Study." Journal of Nepal Health Research Council 17, no. 01 (April 28, 2019): 90–93. http://dx.doi.org/10.33314/jnhrc.v17i01.2012.
Abstract:
Background: Right hepatic duct, formed by the confluence of the anterior and posterior right sectorial ducts, joins left hepatic duct to form common hepatic duct. This fashion of confluence does not prevail in all cases. The sectorial ducts can aberrantly meet left duct and rest of the ducts from the left lobe of liver. Presence of such variation imposes clinical importance during peri-hilar, split liver transplant surgery or cholecystectomy. Nepalese population has not been explored before disregarding clinical necessity as MRI or cholangiography. Methods: Descriptive cross sectional study was conducted in 107 cases dissecting the main portal fissure separating hemi liver and extrahepatic biliary confluences. Methylene blue dye was injected and bile duct wall was cut open to the study pattern of the confluence. Data analysis was done with Statistical Package for Social Sciences (SPSS) version 17.Results: Normal variant of confluence was found in 72% cases, aberrant right posterior sectorial duct joins left hepatic duct in 9.3% and aberrant right anterior duct or low insertion of the right posterior sectorial duct was found in 1.9%. 9.3% of cases there is no true right hepatic duct often described as triple confluence. 0.9% cases showed no particular pattern of confluence where common hepatic duct is formed by multiple confluence. Quadrate lobe was found to be draining into right anterior sectorial duct in a single case.Conclusions: Right hepatic duct confluence pattern is variable and all the evidence occurs at the main portal fissure. Right sectorial duct may join the left duct avoiding normal confluence pattern. Right posterior sectorial duct may be inserted low in the common bile duct.Keywords: Duct; hepatic; sectorial; variation.
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Тамм, Т. И., И. Г. Зульфигаров, И. Н. Мамонтов, К. А. Крамаренко, А. П. Захарчук, О. М. Решетняк, and А. Т. Устинов. "Peculiarities of Liver Histostructure and Choledochous Duct in Partially Restored Bile Duct." Хирургия. Восточная Европа, no. 4 (December 31, 2021): 452–59. http://dx.doi.org/10.34883/pi.2021.10.4.013.
Abstract:
Введение. Состояние гистоструктуры печени при полной непроходимости желчных путей достаточно полно отражено в литературе. За последние десятилетия нами не найдено публикаций, посвященных изучению динамики гистологической структуры печени и стенки холедоха при частично восстановленном токе желчи, но неустраненной причине холестаза. Цель. Определить в эксперименте динамику гистологической структуры печени и стенки холедоха при восстановленном токе желчи, но неустраненной причине полной обструкции. Материалы и методы. Моделирование было выполнено на 29 крысах линии Вистар путем выделения холедоха и его перевязки без пересечения. Животных выводили из эксперимента на 3, 7, 14, 21 и 35-е сутки, когда производили забор биоптатов печени и холедоха для изучения их гистологической структуры. Результаты. На 3-и сутки отмечены процессы деструкции гепатоцитов, одновременно с этим наблюдалась начинающаяся пролиферация желчных протоков. На 7-е сутки в 12-перстной кишке у части животных обнаружена желчь, а в печени отмечено уменьшение острого воспаления в виде снижения полнокровия сосудов и лейкоцитарной инфильтрации, а также появились признаки новообразованных желчных протоков. Процессы более полной реканализации желчных путей с восстановлением пассажа желчи начинаются с 14-х суток. На 35-е сутки у 2/3 животных восстанавливался пассаж желчи, что подтверждено ее наличием в 12-перстной кишке. В печени с 14-х по 28-е сутки стихали процессы воспаления и формировалась дольковая архитектоника с невыраженными процессами фиброза. Наиболее ярко это было представлено на 35-е сутки исследования. Одновременно с этим в стенке холедоха начиная с 3-х суток выше лигатуры отмечены морфологические изменения в виде острого катарального воспаления с переходом во флегмонозное. На фоне процессов воспаления в стенке холедоха происходят процессы восстановления желчетока за счет появления вновь образованных желчных протоков. К 35-м суткам у животных с наличием желчи в 12-перстной кишке выявлена правильная дольковая архитектоника в структуре печени с невыраженным процессом фиброза. В стенке холедоха, расположенного выше места препятствия, в эти сроки на фоне уменьшения воспаления и слабого фиброза выявлено множество новообразованных желчных протоков. Выводы. При полной обструкции желчных путей в эксперименте в печеночной дольке происходят некротические изменения, которые регрессируют по мере устранения холестаза. Восстановление тока желчи при неустраненной причине ведет к нормализации гистологической структуры печени. В стенке холедоха при полной его обструкции развивается катаральное с переходом в флегмонозное воспаление. С течением времени у животных происходит реканализация холедоха за счет вновь образованных желчных ходов в его стенке. Introduction. The state of the histostructure of the liver with complete obstruction of the biliary tract is fully reflected in the literature. Over the past decades, we have not found publications devoted to the study of the dynamics of the histological structure of the liver and the wall of the common bile duct with partially restored bile flow, but the cause of cholestasis has not been eliminated. Purpose. To determine in an experiment the dynamics of the histological structure of the liver and the wall of the common bile duct with a restored bile flow, but not eliminated the cause of complete obstruction. Materials and methods. Modeling was performed on 29 Wistar rats by isolating the choledochous duct and ligating it without crossing it. The animals were taken out of the experiment on days 3, 7, 14, 21 and 35, when biopsies of the liver and common bile duct were taken to study their histological structure. Results. On the 3rd day, the processes of destruction of hepatocytes were noted, at the same time, the beginning proliferation of the bile ducts was observed. On the 7th day, bile was found in the duodenum 12 in some animals, and a decrease in acute inflammation in the form of a decrease in vascular congestion and leukocyte infiltration was noted in the liver, as well as signs of newly formed bile ducts. The processes of a more complete recanalization of the biliary tract with the restoration of the passage of bile begin from 14 days. On the 35th day, bile passage was restored in 2/3 of the animals, which was confirmed by its presence in the duodenum 12. In the liver from 14 to 28 days, inflammation processes subsided and lobular architectonics with unexpressed fibrosis processes were formed. This was most vividly presented on the 35th day of the study. At the same time, in the wall of the common bile duct, starting from 3 days above the ligature, morphological changes were noted in the form of acute catarrhal inflammation with a transition to phlegmonous. Against the background of the processes of inflammation in the wall of the common bile duct, the processes of restoration of the bile duct occur due to the appearance of the newly formed bile ducts. By the 35th day, animals with bile in the duodenum 12 showed the correct lobular architectonics in the structure of the liver with an unexpressed process of fibrosis. In the wall of the common bile duct, located above the place of the obstacle, during these periods, against the background of a decrease in inflammation and weak fibrosis, a lot of newly formed bile ducts were revealed. Conclusions. With complete obstruction of the biliary tract in the experiment, necrotic changes occur in the hepatic lobule, which regress as cholestasis is eliminated. Restoration of bile flow with an unresolved cause leads to the normalization of the histological structure of the liver. In the wall of the common bile duct, with its complete obstruction, catarrhal develops with a transition to phlegmonous inflammation. With the passage of time in animals, the common bile duct is recanalized due to the newly formed bile ducts in its wall.
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Sui, Xiuming, Wei Zhao, Xiaolei Sun, Weiwei Luo, and Qingjun Zhao. "Aerodynamic performance analysis and optimization of a turbine duct with low degree of partial admission." Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering 232, no. 5 (February 19, 2017): 988–1001. http://dx.doi.org/10.1177/0954410017691068.
Abstract:
A partial admission turbine duct with outlet-to-inlet area ratio greater than unity can increase the admission degree of the downstream turbine stage and, thus improve the performance of a multistage turbine with a low partial admission degree. However, the upstream flow structures of ducts, such as secondary flow, especially the circumferential nonuniformities originating from the effect of the partial admission, make the flow in ducts complex. The complexity of the flow has a negative impact on the performance of ducts. In the present investigation, numerical study of the flow behavior within ducts is done to evaluate the effect of the partial admission on the performance of the ducts. The study is carried out with regard to two cases, i.e. which are with the same duct geometry but are at different working conditions to highlight the impact of partial admission on the performance of ducts. Case 1 is used as baseline. It is designed based on circumferential mass-averaged flow conditions at ducts inlet. It causes the circumferential nonuniformities originating from the partial admission to have no impact on the performance of case 1. Case 2, which considers partial admission, is compared with case 1 to know the impact of the partial admission on the performance of ducts, and to give guidelines to design a duct for the partial admission turbines. Since the duct inlet conditions is a result of the interaction between partial admission turbine and duct, a straightforward way to consider the effect of the partial admission is to simulate the flows in ducts and upstream turbines contemporaneously. Comparative results indicate that the mixing of main flow in the admitted channel and the windage fluid from the unadmitted channel occurs at the duct inlet close to the duct circumferential wall. The adverse pressure gradient of case 2 in that region becomes larger than that of case 1. As a result, the flow separates at that region deteriorating the performance of ducts. Based on the simulation results of the previous cases, case 2’s circumferential wall surface, which is along the gas swirling direction is shrunk to accelerate the flow and, thereby, overcome the adverse pressure gradient imposed by the effect of the partial admission. The results show that the separation is restrained and the decrease in total pressure loss is 52.9%.
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Santos, F. Rodrigues, G. da Silva Costa, A. T. da Cunha Lima, M. P. de Almeida, and I. C. da Cunha Lima. "Detection of memory loss of symmetry in the blockage of a turbulent flow within a duct." International Journal of Modern Physics C 28, no. 06 (April 28, 2017): 1750079. http://dx.doi.org/10.1142/s0129183117500796.
Abstract:
This paper aims to detect memory loss of the symmetry of blockades in ducts and how far the information on the asymmetry of the obstacles travels in the turbulent flow from computational simulations with OpenFOAM. From a practical point of view, it seeks alternatives to detect the formation of obstructions in pipelines. The numerical solutions of the Navier–Stokes equations were obtained through the solver PisoFOAM of the OpenFOAM library, using the large Eddy simulation (LES) for the turbulent model. Obstructions were placed near the duct inlet and, keeping the blockade ratio fixed, five combinations for the obstacles sizes were adopted. The results show that the information about the symmetry is preserved for a larger distance near the ducts wall than in mid-channel. For an inlet velocity of 5[Formula: see text]m/s near the walls the memory is kept up to distance 40 times the duct width, while in mid-channel this distance is reduced almost by half. The maximum distance in which the symmetry breaking memory is preserved shows sensitivity to Reynolds number variations in regions near the duct walls, while in the mid channel that variations do not cause relevant effects to the velocity distribution.
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Du, Dong Xing, Fa Hu Zhang, Dian Cai Geng, and Ying Ge Li. "Numerical Study on Film Foam Flow Characteristics in a Straight Duct." Key Engineering Materials 561 (July 2013): 472–77. http://dx.doi.org/10.4028/www.scientific.net/kem.561.472.
Abstract:
Straight ducts capture some essential features of the motion of foam in porous media in petroleum industry. In this paper, Surface Evolver was employed to build the mathematical model to study the flow behavior of lamellas in the duct with different models. Numerical results show good agreement with experiments and some important features of lamella flow behavior in straight ducts are obtained. It is concluded that, the physical model with viscous force can adequately describe the flow characteristics of reality foam in the experiment. The actual pressure difference consists of the pressure difference caused by the curvature of the lamellas and the drag force on the boundary wall. Under the ideal condition of without drag force along the wall, the pressure drop for lamella flow in the duct is zero, and the shape and the velocity of the lamellas will maintain constant.
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Goto, Tomonobu, Kuri Maeda, Tonau Nakai, and Masaharu Nishimura. "Acoustic modes in a rectangular flow duct with a wall of finite acoustic impedance value." INTER-NOISE and NOISE-CON Congress and Conference Proceedings 268, no. 7 (November 30, 2023): 1055–65. http://dx.doi.org/10.3397/in_2023_0161.
Abstract:
The acoustic field in a rectangular flow duct of infinite length was numerically investigated. One of the walls of the duct was assumed to have finite acoustic impedance while the other three were rigid walls. Uniform flow profile was also assumed. The propagation constants, namely, complex wave numbers, were calculated for various impedance values and the Mach numbers of the flow from the boundary condition on the finite impedance wall derived by Myers. First, we calculated the propagation constant without uniform flow. If all four walls are rigid and the frequency of the sound is under the cut-off frequency, only zeroth mode propagates along the duct and higher modes decay rapidly. In contrast, if one wall has a finite impedance value, two modes can have comparable amount of attenuation. The acoustic field in the duct would be a superposition of those less decaying modes depending on the inlet condition. As for the flow effect, the attenuation tends to be decreasing in fair wind, and vice versa. This tendency, however, is not general because the propagation constant moves on the complex plane in intricate manner.
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Yoganandh, M., Jade Nagaraja, and B. Venkatesham. "Prediction of insertion loss of lagging in rectangular duct using statistical energy analysis." Noise Control Engineering Journal 67, no. 6 (November 1, 2019): 438–46. http://dx.doi.org/10.3397/1/376740.
Abstract:
In this article, statistical energy analysis (SEA) is used to predict insertion loss from a lagged rectangular HVAC duct. For a lagged duct, all duct walls are treated from outside with acoustic material. Although deterministic methods like the finite element method (FEM), boundary element method (BEM), and wave based methods can predict the breakout noise, these methods have limitations in handling systems with high modal density due to higher computational cost. In this study, a rectangular duct is divided into six subsystems, which are four duct walls (each wall considered as a subsystem), internal air cavity and external airspace. Power flow analysis is performed on all subsystems to calculate transverse transmission loss of an unlined duct and insertion loss for a lagged duct. Predicted transverse transmission loss values are validated with ASHRAE data and Insertion loss values with literature. The results obtained are in good agreement.
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Indu, N. R., Hiremath P. B, M. Reshmi, M. Sree Supriya, and Reshma Hiremath. "Case report of a huge Gartner’s cyst." Indian Journal of Obstetrics and Gynecology Research 10, no. 1 (February 15, 2023): 67–69. http://dx.doi.org/10.18231/j.ijogr.2023.014.
Abstract:
Gartner’s cyst accounts for 11% of all vaginal cysts. It results from total or partial occlusion of Gartner’s duct, the mesonephric duct remainder. It is often located in the anterior or lateral wall of the vagina from the cervix to the introitus, however it has exceptionally been described in the posterior location also.It is typically small and asymptomatic and occurs along the lateral walls of the vagina, following the course of the Gartner’s duct. Rarely it can be congenital., , ,
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Kim, Yeseul, Min Jung Jung, and Su-Jin Shin. "Heterotopic Gastric Mucosa in the Common Bile Duct With Cholangiocarcinoma." International Journal of Surgical Pathology 26, no. 8 (May 10, 2018): 745–48. http://dx.doi.org/10.1177/1066896918775531.
Abstract:
Gastric heterotopia within the biliary system is extremely rare. Moreover, the combination of gastric heterotopia in the bile duct with cholangiocarcinoma has not been reported. We describe a case of heterotopic gastric mucosa in the common bile duct with cholangiocarcinoma. An 80-year-old male was admitted with abdominal pain. Abdominal computed tomography revealed wall thickening from the hilar duct to the distal common bile duct. Biopsy from the distal bile duct showed only benign gastric foveolar-type epithelium and fundic glands. Although the diagnosis of the biopsy was benign, malignancy was strongly suspected from the radiologic findings, and excision of the bile ducts was performed. Microscopically, the resected specimen showed poorly formed malignant glands and gastric heterotopia also identified in the common bile duct. Three months later, the patient’s state worsened due to recurrence, and he died. To our knowledge, this is the first report of gastric heterotopia in the bile duct accompanying cholangiocarcinoma.
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Pazderka, Jiří, Eva Hájková, and Martin Jiránek. "UNDERGROUND AIR DUCT TO CONTROL RISING MOISTURE IN HISTORIC BUILDINGS: IMPROVED DESIGN AND ITS DRYING EFFICIENCY." Acta Polytechnica 57, no. 5 (October 31, 2017): 331. http://dx.doi.org/10.14311/ap.2017.57.0331.
Abstract:
The underground air ducts along peripheral walls of a building are a remediation method, which principle is to enable an air flow along the moist building structure’s surface to allow a sufficient evaporation of moisture from the structure. This measure reduces the water transport (rising moisture) into the higher parts of the wall where the high water content in masonry is undesirable. Presently, underground air ducts are designed as masonry structures, which durability in contact with ground moisture is limited. The article describes a new design of an underground air duct, which is based on specially shaped concrete blocks (without wet processes, because the blocks are completely precast). The air duct from concrete blocks is situated completely below the ground surface (exterior) or below the floor (interior). Thanks to this, the system is invisible and does not disturb the authentic look of rehabilitated historic buildings. The efficiency of the air duct technical solution was verified by the results of tests (based on the measured moisture values) conducted on a laboratory model. The experimental study showed that the moisture in the masonry equipped with the presented underground air duct had decreased considerably compared to the reference sample, namely by 43 % on average. The experimental study was numerically validated through numerical simulations performed with the program WUFI 2D.
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Lawal, A. "Mixed Convection Heat Transfer to Power Law Fluids in Arbitrary Cross-Sectional Ducts." Journal of Heat Transfer 111, no. 2 (May 1, 1989): 399–406. http://dx.doi.org/10.1115/1.3250691.
Abstract:
An analytical investigation of three-dimensional mixed convection flow and heat transfer to power-law fluids in horizontal arbitrary cross-sectional ducts is undertaken. The continuity equation and parabolic forms of the energy and momentum equations in rectangular coordinates are transformed into new orthogonal coordinates with the boundaries of the duct coinciding with the coordinate surfaces. The transformed equations are solved by the finite difference technique. The fluid enters the duct with constant velocity and temperature profiles with the wall of the duct subjected to constant temperature. Local heat transfer coefficients and pressure drop for several values of Gr/Re and power-law index n are computed for the triangular, square, trapezoidal, pentagonal, and circular ducts. The buoyancy force is found to increase both the Nusselt number and the pressure drop.
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Ali, Mohamed E. "Natural Convection Heat Transfer From Horizontal Rectangular Ducts." Journal of Heat Transfer 129, no. 9 (December 2, 2006): 1195–202. http://dx.doi.org/10.1115/1.2739623.
Abstract:
Experimental investigations have been reported on steady state natural convection from the outer surface of horizontal ducts in air. Five ducts have been used with aspect ratios (Γ=duct height/duct width) of 2, 1, and 0.5. The ducts are heated using internal constant heat flux heating elements. The temperatures along the surface and peripheral directions of the duct wall are measured. Longitudinal (circumference averaged) heat transfer coefficients along the side of each duct are obtained for laminar and transition regimes of natural convection heat transfer. Total overall averaged heat transfer coefficients are also obtained. Longitudinal (circumference averaged) Nusselt numbers are evaluated and correlated using the modified Rayleigh numbers for transition regime using the axial distance as a characteristic length. Furthermore, total overall averaged Nusselt numbers are correlated with the modified Rayleigh numbers, the aspect ratio, and area ratio for the laminar and transition regimes. The longitudinal or total averaged heat transfer coefficients are observed to decrease in the laminar region and to increase in the transition region. Laminar regimes are obtained only at very small heat fluxes, otherwise, transitions are observed.
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Liou, Tong-Miin, Meng-Yu Chen, and Yu-Ming Wang. "Heat Transfer, Fluid Flow, and Pressure Measurements Inside a Rotating Two-Pass Duct With Detached 90-Deg Ribs." Journal of Turbomachinery 125, no. 3 (July 1, 2003): 565–74. http://dx.doi.org/10.1115/1.1565086.
Abstract:
Transient thermochromic liquid crystal thermography, a laser-Doppler velocimeter, and pressure transducers have been used to measure the local heat transfer, velocity, and wall static-pressure distributions, respectively, in a rotating two-pass square duct with 90-deg ribs detached from the leading and trailing walls. The ribs were square in cross-section and their detached-distance/height ratio was 0.38. The rib-height/duct-height ratio and the pitch/rib-height ratio were 0.136 and 10, respectively. The duct Reynolds number was 1×104 and rotation number ranged from 0 to 0.2. Results are compared with attached rib cases in terms of regional averaged Nusselt number, transverse mean velocity component, pressure coefficient distributions and variation of friction factor with rotation number. The competition between convection effect of the wall jet and downwash effect of the rib-top separated shear layer on the heat transfer augmentation is addressed in detail. Discussion on local Nusselt number distribution, mean velocity components, and turbulent kinetic energy is included. Simple expressions are obtained to correlate friction factor with rotation number. Rib detachment is found to enhance heat transfer on the leading wall of the first outward pass and on the trailing wall of the second inward pass over as compared to the attached rib case. The trend is reversed on the other two walls. Nevertheless, detached ribs create more uniform heat transfer distributions on the leading and trailing walls than attached ribs.
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Baumeister, K. J., and K. L. Kreider. "Finite Difference Time Marching in the Frequency Domain: A Parabolic Formulation for the Convective Wave Equation." Journal of Vibration and Acoustics 118, no. 4 (October 1, 1996): 622–29. http://dx.doi.org/10.1115/1.2888344.
Abstract:
An explicit finite difference iteration scheme is developed to study harmonic sound propagation in ducts. To reduce storage requirements for large 3D problems, the time dependent potential form of the acoustic wave equation is used. To insure that the finite difference scheme is both explicit and stable, time is introduced into the Fourier transformed (steady-state) acoustic potential field as a parameter. Under a suitable transformation, the time dependent governing equation in frequency space is simplified to yield a parabolic partial differential equation, which is then marched through time to attain the steady-state solution. The input to the system is the amplitude of an incident harmonic sound source entering a quiescent duct at the input boundary, with standard impedance boundary conditions on the duct walls and duct exit. The introduction of the time parameter eliminates the large matrix storage requirements normally associated with frequency domain solutions, and time marching attains the steady-state quickly enough to make the method favorable when compared to frequency domain methods. For validation, this transient-frequency domain method is applied to sound propagation in a 2D hard wall duct with plug flow.